Life is unpredictable, love is complicated and will make you sick with happiness and nauseous from despair, and children will change everything you know about being an adult in an instant. And try as you might, there is nothing you can control about what fate may have laying in wait for you around the next corner. However, Maggie (Greta Gerwig) is determined to make her own happiness, rather than wait for circumstance to serve it up for her. As the title for writer/director Rebecca Miller’s latest suggests, her character is doing what she can to play both sides of the metaphorical checkers board, but she’ll soon learn that life is more like a chess game where you’re consistently three moves behind.

Successful in her career, with a teaching gig at The New School, Maggie is unlucky when it comes to relationships, lamenting to her ex-boyfriend and best pal Tony (Bill Hader) that her relationships never last more than six months. However, she wants to start a family, and she’s not just going to wait around and hope that she eventually finds the right person to start one with. Instead, she turns to math genius turned artisanal pickle entrepreneur Guy (Travis Fimmel) to provide the seed so she can step into motherhood all on her own.

However, a curveball arrives in the shape of John (Ethan Hawke), a new professor at Maggie’s school who’s teaching Ficto-critical Anthropology, and according to Tony’s wife Felicia (Maya Rudolph), who also works at The New School, something of a hunky “panty melter.” Indeed, a meetcute in HR between John and Maggie marks the first spark of what turns into an intellectual affair (John has Maggie critique his first novel) and eventually a physical one. Passion soon overrules logic for both John and Maggie. The former ends his marriage with Danish critical theorist Georgette (Julianne Moore), splitting up his family which includes two kids in the process, to take up with Maggie, where they quickly have a new child. But nothing ever ends cleanly, particularly when kids, careers, ambitions, and relationships connect and collide, and to Maggie’s surprise, she soon realizes she’s not as fulfilled as she thought. And perhaps more intriguingly, the power to change things might be out of her hands.

Witty, observational, and hilarious, “Maggie’s Plan” is the kind of richly complex dramedy that proves to be the rare picture that serves both halves of that genre description fully, equally, and satisfyingly. It’s Gerwig who carries the movie, and while some may scoff she’s simply playing a variation on a type we’ve seen from her in “Frances Ha” and “Mistress America,” that would be a tremendous disservice to both her work and Miller’s direction. Unlike her much more frantic pictures with Noah Baumbach, even with a trim ninety-minute running time, Miller’s picture moves with a gentle momentum.

And with added latitude and breathing room to play out the scenes, Gerwig shades Maggie into so much more than just a harried career woman, suddenly trying to sort out marriage and motherhood. Maggie isn’t burdened so much as baffled by what it actually means to share a life, home, and child with someone, and navigates it imperfectly, but passionately, with great love for her daughter, and admiration for her husband, but also yearning for her own needs. It’s terrifically written material wisely played out with great care by Miller; this is a filmmaker who isn’t exploiting her characters for laughs, but cares for them enough that the situations in which they are placed for both humor and heartbreak are earned and effective.

And that consideration is spread out across the entire ensemble. Audiences may wind up the most divided about John — nicely portrayed in a subtle but evolving performance by Hawke — whose selfishness seems to metastatize the longer he’s with Maggie. And where most screenwriters would take the easy road to portray him as the villain of sorts, Miller’s insightful screenplay refuses to corner him. And the same goes for Moore, whose frosty Georgette melts into something far more vulnerable in the later stages of the film. Elsewhere, Hader and Rudolph are delightful together, with their characters believably in the kind of huge-hearted, love filled, bickering marriage that they couldn’t have another way. All around, the screenplay affords the actors the chance to play flawed and funny, and the cast seizes the opportunity to turn genre tropes on its head.

The “Frances Ha”/”Mistress America” comparisons won’t be helped by having those film’s cinematographer Sam Levy shooting “Maggie’s Plan” as well, but his work is arguably more sophisticated here. Where Baumbach’s pictures are slices of a particular moment in a young woman’s life, Miller’s film takes a different approach, spread across a few years, and with that comes slightly more dramatic weight. And visually, Levy follows suit, and most impressive is his smooth transition to handheld during some key closeups, which really assist “Maggie’s Plan” in making some big swings from drama to comedy and back (or vice versa) at key moments during the movie. Miller’s direction and Levy’s unfussy but intelligently executed work behind the camera allows those transitions to often move with great harmony.

As it unfolds, “Maggie’s Plan” gives us the kind of intriguingly misguided but good-hearted characters that make us want to know what happens to them ten or fifteen years down the line. And it’s the kind of movie that promises to resonate entirely differently as the viewer’s life experience changes too. Terrifically drawn, I’m fascinated to find out if my sympathies and perceptions of Maggie, John, and Georgette will differ down the road, of if they’ll have learned that theoretical thinking and matters of the heart are two totally different things. Time will tell, but right now, they are making a terrific, heartbreaking and heartwarming mess of everything. [B+]